Openeo-aggregator

- Add `AggregatorBackendConfig.aggregator_backends` and deprecate `AggregatorConfig.aggregator_backends` ([112](https://github.com/Open-EO/openeo-aggregator/issues/112))

- Eliminate unused `AggregatorConfig.configured_oidc_providers` ([112](https://github.com/Open-EO/openeo-aggregator/issues/112))

- Add `AggregatorBackendConfig` to `conf/aggregator.*.py` files ([112](https://github.com/Open-EO/openeo-aggregator/issues/112))

- move `connections_cache_ttl` config to AggregatorBackendConfig ([112](https://github.com/Open-EO/openeo-aggregator/issues/112))
- replace `kazoo_client_factory` config with `zk_memoizer_tracking` ([112](https://github.com/Open-EO/openeo-aggregator/issues/112))
- Add `AggregatorBackendConfig.zookeeper_prefix` and deprecate `AggregatorConfig.zookeeper_prefix` ([112](https://github.com/Open-EO/openeo-aggregator/issues/112))

- Support regexes in `collection_whitelist` config (eu-cdse/openeo-cdse-infra54)

- Move `collection_whitelist` config to `AggregatorBackendConfig` ([112](https://github.com/Open-EO/openeo-aggregator/issues/112))